Flow behavior and mixing of single-phase laminar Newtonian miscible fluid in T-junction micromixer with twisted mixing channel - A numerical study

Abstract

The interest in static T-junction micromixers has increased in recent years due in part to their compact design, high area-to-volume ratio, and the absence of moving parts. The microfluidic mixing typically occurs in the laminar regime at low Reynolds numbers, which leads to a low mixing performance. The mixing rate is mainly affected by molecular diffusion and the impinging of two opposite streams. To create more significant secondary and swirling flows to enhance the performance, a twisted mixing channel is proposed in combination with a pulsation inlet. A 3D numerical model is developed and validated based on the fluid dynamics to study the flow behavior and the mixing performance of single-phase mixing of laminar Newtonian miscible fluid for this innovative passive micromixer design. To compare the different designs, a parameter called performance index is defined as the fluid mixing index per unit friction factor of the mixer. The effect of the number of twists in the mixing channel, inlet Reynolds number and Schmidt number on the mixing performance is assessed through numerical investigation to gain a comprehensive understanding of the proposed design. Furthermore, the effect of pulsation is evaluated by introducing a sinusoidal velocity profile at the inlet. For pulsation inlet, it was found that a phase difference between inlet 1 and inlet 2 is required to achieve considerable mixing index performance. The overall results indicate the promising potential of the proposed design for micromixers which offers considerable improvement in the mixing while imposing only a marginal increase in the pressure drop. Moreover, the simple design of this mixer makes it a realistic solution for industrial applications.